402 lines
19 KiB
Python
402 lines
19 KiB
Python
"""MCP client-side handlers for server-initiated requests: sampling
|
|
(sampling/createMessage, text and tool-use results) and elicitation."""
|
|
|
|
import asyncio
|
|
import json
|
|
import logging
|
|
import time
|
|
from typing import Callable, List, Optional
|
|
from tools.mcp_tool_common import _MISSING, _exc_str, _safe_numeric, _sanitize_error, mcp_field, _core
|
|
from tools.mcp_tool_schema import _normalize_mcp_input_schema
|
|
|
|
logger = logging.getLogger("tools.mcp_tool")
|
|
|
|
|
|
def _tool_use_id(block):
|
|
"""Tool-use id (the discriminator for a tool *result* block), read under both
|
|
SDK spellings — on mcp 2.x a bare ``hasattr(b, "toolUseId")`` is False and
|
|
would silently drop tool results."""
|
|
return mcp_field(block, "tool_use_id", "toolUseId", _MISSING)
|
|
|
|
|
|
def _is_tool_use(block) -> bool:
|
|
return hasattr(block, "name") and hasattr(block, "input")
|
|
|
|
|
|
def _tool_result_text(block) -> str:
|
|
"""Text of a ToolResultContent block ("" when it carries no content)."""
|
|
content = getattr(block, "content", None)
|
|
if content is None:
|
|
return ""
|
|
items = content if isinstance(content, list) else [content]
|
|
return "\n".join(item.text for item in items if hasattr(item, "text"))
|
|
|
|
|
|
def _content_part(block) -> Optional[dict]:
|
|
"""One OpenAI content part for a text/image block; None when unsupported."""
|
|
if hasattr(block, "text"):
|
|
return {"type": "text", "text": block.text}
|
|
mime = mcp_field(block, "mime_type", "mimeType", _MISSING)
|
|
if hasattr(block, "data") and mime is not _MISSING:
|
|
return {"type": "image_url", "image_url": {"url": f"data:{mime};base64,{block.data}"}}
|
|
logger.warning("Unsupported sampling content block type: %s (skipped)", type(block).__name__)
|
|
return None
|
|
|
|
|
|
def _tool_call_dict(tu, index: int) -> dict:
|
|
args = tu.input
|
|
return {
|
|
"id": getattr(tu, "id", f"call_{index}"),
|
|
"type": "function",
|
|
"function": {
|
|
"name": tu.name,
|
|
"arguments": json.dumps(args, ensure_ascii=False) if isinstance(args, dict) else str(args),
|
|
},
|
|
}
|
|
|
|
|
|
def _convert_sampling_message(msg) -> List[dict]:
|
|
"""One MCP SamplingMessage -> OpenAI-format messages (tool results first,
|
|
then either an assistant tool_calls message or plain content)."""
|
|
blocks = msg.content_as_list if hasattr(msg, "content_as_list") else (
|
|
msg.content if isinstance(msg.content, list) else [msg.content]
|
|
)
|
|
tool_results = [b for b in blocks if _tool_use_id(b) is not _MISSING]
|
|
tool_uses = [b for b in blocks if _is_tool_use(b) and _tool_use_id(b) is _MISSING]
|
|
content_blocks = [b for b in blocks if _tool_use_id(b) is _MISSING and not _is_tool_use(b)]
|
|
|
|
out = [{"role": "tool", "tool_call_id": _tool_use_id(tr), "content": _tool_result_text(tr)} for tr in tool_results]
|
|
if tool_uses:
|
|
msg_dict: dict = {"role": msg.role, "tool_calls": [_tool_call_dict(tu, i) for i, tu in enumerate(tool_uses)]}
|
|
text_parts = [b.text for b in content_blocks if hasattr(b, "text")]
|
|
if text_parts:
|
|
msg_dict["content"] = "\n".join(text_parts)
|
|
out.append(msg_dict)
|
|
elif content_blocks:
|
|
if len(content_blocks) == 1 and hasattr(content_blocks[0], "text"):
|
|
out.append({"role": msg.role, "content": content_blocks[0].text})
|
|
else:
|
|
parts = [p for p in map(_content_part, content_blocks) if p is not None]
|
|
if parts:
|
|
out.append({"role": msg.role, "content": parts})
|
|
return out
|
|
|
|
|
|
def _parse_tool_call_arguments(server_name: str, args) -> dict:
|
|
"""LLM tool_calls arguments -> dict; malformed JSON / non-dict values are
|
|
wrapped as ``{"_raw": ...}`` rather than dropped."""
|
|
if isinstance(args, str):
|
|
try:
|
|
return json.loads(args)
|
|
except (json.JSONDecodeError, ValueError):
|
|
logger.warning(
|
|
"MCP server '%s': malformed tool_calls arguments from LLM (wrapping as raw): %.100s",
|
|
server_name, args,
|
|
)
|
|
return {"_raw": args}
|
|
return args if isinstance(args, dict) else {"_raw": str(args)}
|
|
|
|
|
|
def _response_total_tokens(response, default):
|
|
return getattr(getattr(response, "usage", None), "total_tokens", default)
|
|
|
|
|
|
class SamplingHandler:
|
|
"""Handles sampling/createMessage requests for one MCP server; passed to
|
|
``ClientSession`` as ``sampling_callback``. All state (rate-limit
|
|
timestamps, metrics, tool-loop counter) is per instance. Runs on the MCP
|
|
background loop; the sync LLM call is offloaded via ``asyncio.to_thread``.
|
|
|
|
Deprecated upstream (MCP 2026-07-28, SEP-2577, 12-month window): stays fully
|
|
functional because handshake-era servers still issue it, but do NOT grow new
|
|
capability here — modern servers use MRTR, handled by the SDK session layer.
|
|
"""
|
|
|
|
_STOP_REASON_MAP = {"stop": "endTurn", "length": "maxTokens", "tool_calls": "toolUse"}
|
|
_LOG_LEVELS = {"debug": logging.DEBUG, "info": logging.INFO, "warning": logging.WARNING}
|
|
|
|
def __init__(self, server_name: str, config: dict):
|
|
self.server_name = server_name
|
|
self.max_rpm = _safe_numeric(config.get("max_rpm", 10), 10, int)
|
|
self.timeout = _safe_numeric(config.get("timeout", 30), 30, float)
|
|
self.max_tokens_cap = _safe_numeric(config.get("max_tokens_cap", 4096), 4096, int)
|
|
self.max_tool_rounds = _safe_numeric(config.get("max_tool_rounds", 5), 5, int, minimum=0)
|
|
self.model_override = config.get("model")
|
|
self.allowed_models = config.get("allowed_models", [])
|
|
self.audit_level = self._LOG_LEVELS.get(str(config.get("log_level", "info")).lower(), logging.INFO)
|
|
self._rate_timestamps: List[float] = []
|
|
self._tool_loop_count = 0
|
|
self.metrics = {"requests": 0, "errors": 0, "tokens_used": 0, "tool_use_count": 0}
|
|
|
|
def _check_rate_limit(self) -> bool:
|
|
"""Sliding-window (60s) limiter; True if the request is allowed."""
|
|
now = time.time()
|
|
self._rate_timestamps[:] = [t for t in self._rate_timestamps if t > now - 60]
|
|
if len(self._rate_timestamps) >= self.max_rpm:
|
|
return False
|
|
self._rate_timestamps.append(now)
|
|
return True
|
|
|
|
def _resolve_model(self, preferences) -> Optional[str]:
|
|
"""Config override > server hint > None (use default)."""
|
|
if self.model_override:
|
|
return self.model_override
|
|
for hint in (getattr(preferences, "hints", None) or []):
|
|
if getattr(hint, "name", None):
|
|
return hint.name
|
|
return None
|
|
|
|
def _convert_messages(self, params) -> List[dict]:
|
|
"""Convert MCP SamplingMessages to OpenAI format (``content_as_list``
|
|
when the SDK provides it; per-block duck-typed dispatch)."""
|
|
return [m for msg in params.messages for m in _convert_sampling_message(msg)]
|
|
|
|
@staticmethod
|
|
def _error(message: str, code: int = -1):
|
|
"""Return ErrorData (MCP spec) or raise as fallback."""
|
|
if _core._MCP_SAMPLING_TYPES:
|
|
return _core.ErrorData(code=code, message=message)
|
|
raise Exception(message)
|
|
|
|
def _fail(self, message: str):
|
|
"""Count an error and return the ErrorData for it."""
|
|
self.metrics["errors"] += 1
|
|
return self._error(message)
|
|
|
|
def _log_response(self, response, suffix: str = "", *args) -> None:
|
|
logger.log(
|
|
self.audit_level, "MCP server '%s' sampling response: model=%s, tokens=%s" + suffix,
|
|
self.server_name, response.model, _response_total_tokens(response, "?"), *args,
|
|
)
|
|
|
|
def _build_tool_use_result(self, choice, response):
|
|
"""Build a CreateMessageResultWithTools from an LLM tool_calls response,
|
|
subject to tool-loop governance (``max_tool_rounds``; 0 disables)."""
|
|
self.metrics["tool_use_count"] += 1
|
|
if self.max_tool_rounds == 0:
|
|
self._tool_loop_count = 0
|
|
return self._error(f"Tool loops disabled for server '{self.server_name}' (max_tool_rounds=0)")
|
|
self._tool_loop_count += 1
|
|
if self._tool_loop_count > self.max_tool_rounds:
|
|
self._tool_loop_count = 0
|
|
return self._error(
|
|
f"Tool loop limit exceeded for server '{self.server_name}' (max {self.max_tool_rounds} rounds)"
|
|
)
|
|
content_blocks = [
|
|
_core.ToolUseContent(
|
|
type="tool_use", id=tc.id, name=tc.function.name,
|
|
input=_parse_tool_call_arguments(self.server_name, tc.function.arguments),
|
|
)
|
|
for tc in choice.message.tool_calls
|
|
]
|
|
self._log_response(response, ", tool_calls=%d", len(content_blocks))
|
|
return _core.CreateMessageResultWithTools(
|
|
role="assistant", content=content_blocks, model=response.model, stopReason="toolUse",
|
|
)
|
|
|
|
def _build_text_result(self, choice, response):
|
|
"""Build a CreateMessageResult from a normal text response (resets the tool loop)."""
|
|
self._tool_loop_count = 0
|
|
self._log_response(response)
|
|
return _core.CreateMessageResult(
|
|
role="assistant",
|
|
content=_core.TextContent(type="text", text=_sanitize_error(choice.message.content or "")),
|
|
model=response.model,
|
|
stopReason=self._STOP_REASON_MAP.get(choice.finish_reason, "endTurn"),
|
|
)
|
|
|
|
def session_kwargs(self) -> dict:
|
|
"""Kwargs to pass to ClientSession for sampling support."""
|
|
return {
|
|
"sampling_callback": self,
|
|
"sampling_capabilities": _core.SamplingCapability(tools=_core.SamplingToolsCapability()),
|
|
}
|
|
|
|
def _admit(self, params):
|
|
"""Rate-limit + allowed_models gate. Returns ``(resolved_model, None)``
|
|
or ``(None, ErrorData)``."""
|
|
if not self._check_rate_limit():
|
|
logger.warning("MCP server '%s' sampling rate limit exceeded (%d/min)", self.server_name, self.max_rpm)
|
|
return None, self._fail(
|
|
f"Sampling rate limit exceeded for server '{self.server_name}' ({self.max_rpm} requests/minute)"
|
|
)
|
|
model = self._resolve_model(mcp_field(params, "model_preferences", "modelPreferences"))
|
|
resolved_model = model or self.model_override or ""
|
|
if self.allowed_models and resolved_model and resolved_model not in self.allowed_models:
|
|
logger.warning(
|
|
"MCP server '%s' requested model '%s' not in allowed_models", self.server_name, resolved_model,
|
|
)
|
|
return None, self._fail(
|
|
f"Model '{resolved_model}' not allowed for server "
|
|
f"'{self.server_name}'. Allowed: {', '.join(self.allowed_models)}"
|
|
)
|
|
return resolved_model, None
|
|
|
|
def _build_llm_call(self, params, resolved_model: str) -> Callable[[], object]:
|
|
"""Translate the sampling params into a zero-arg sync ``call_llm`` thunk
|
|
(run off-loop so the MCP loop is not blocked)."""
|
|
from agent.auxiliary_client import call_llm
|
|
|
|
messages = self._convert_messages(params)
|
|
system_prompt = mcp_field(params, "system_prompt", "systemPrompt")
|
|
if system_prompt:
|
|
messages.insert(0, {"role": "system", "content": system_prompt})
|
|
max_tokens = min(mcp_field(params, "max_tokens", "maxTokens", self.max_tokens_cap), self.max_tokens_cap)
|
|
temperature = getattr(params, "temperature", None)
|
|
# Forward server-provided tools.
|
|
server_tools = getattr(params, "tools", None)
|
|
tools = [
|
|
{
|
|
"type": "function",
|
|
"function": {
|
|
"name": getattr(t, "name", ""),
|
|
"description": getattr(t, "description", "") or "",
|
|
"parameters": _normalize_mcp_input_schema(mcp_field(t, "input_schema", "inputSchema")),
|
|
},
|
|
}
|
|
for t in server_tools
|
|
] if server_tools else None
|
|
|
|
logger.log(
|
|
self.audit_level,
|
|
"MCP server '%s' sampling request: model=%s, max_tokens=%d, messages=%d",
|
|
self.server_name, resolved_model, max_tokens, len(messages),
|
|
)
|
|
return lambda: call_llm(
|
|
task="mcp", model=resolved_model or None, messages=messages, temperature=temperature,
|
|
max_tokens=max_tokens, tools=tools, timeout=self.timeout,
|
|
)
|
|
|
|
async def __call__(self, context, params):
|
|
"""SDK sampling callback (``SamplingFnT``). Returns CreateMessageResult,
|
|
CreateMessageResultWithTools, or ErrorData."""
|
|
resolved_model, err = self._admit(params)
|
|
if err is not None:
|
|
return err
|
|
sync_call = self._build_llm_call(params, resolved_model)
|
|
try:
|
|
response = await asyncio.wait_for(asyncio.to_thread(sync_call), timeout=self.timeout)
|
|
except asyncio.TimeoutError:
|
|
return self._fail(f"Sampling LLM call timed out after {self.timeout}s for server '{self.server_name}'")
|
|
except Exception as exc:
|
|
return self._fail(f"Sampling LLM call failed: {_sanitize_error(_exc_str(exc))}")
|
|
|
|
# Empty choices happen on content filtering / provider errors.
|
|
if not getattr(response, "choices", None):
|
|
return self._fail(f"LLM returned empty response (no choices) for server '{self.server_name}'")
|
|
|
|
choice = response.choices[0]
|
|
self.metrics["requests"] += 1
|
|
total_tokens = _response_total_tokens(response, 0)
|
|
if isinstance(total_tokens, int):
|
|
self.metrics["tokens_used"] += total_tokens
|
|
if choice.finish_reason == "tool_calls" and getattr(choice.message, "tool_calls", None):
|
|
return self._build_tool_use_result(choice, response)
|
|
return self._build_text_result(choice, response)
|
|
|
|
|
|
def _format_elicitation_schema_summary(schema: dict, server_name: str) -> str:
|
|
"""Render a flat-object requested_schema as a human-readable field list
|
|
(names, types, descriptions) so the user knows what they're approving."""
|
|
props = schema.get("properties") if isinstance(schema, dict) else None
|
|
if not isinstance(props, dict) or not props:
|
|
return f"Approval requested by MCP server '{server_name}'."
|
|
|
|
lines = [f"Fields requested by MCP server '{server_name}':"]
|
|
for field_name, field_spec in props.items():
|
|
spec = field_spec if isinstance(field_spec, dict) else {}
|
|
field_type = str(spec.get("type", "") or "")
|
|
field_desc = str(spec.get("description", "") or "")
|
|
suffix = f" ({field_type})" if field_type else ""
|
|
lines.append(f" - {field_name}{suffix}: {field_desc}" if field_desc else f" - {field_name}{suffix}")
|
|
return "\n".join(lines)
|
|
|
|
|
|
class ElicitationHandler:
|
|
"""Handles ``elicitation/create`` requests for one MCP server; passed to
|
|
``ClientSession`` as ``elicitation_callback``. Form-mode requests route
|
|
through Hermes' approval system (CLI, TUI, Telegram, ...); URL-mode is
|
|
declined as unsupported. Fail-closed: any timeout, exception or unexpected
|
|
state returns decline/cancel, never a silent accept."""
|
|
|
|
# asyncio-side safety net over the approval's own input() timeout so the
|
|
# MCP loop never blocks indefinitely if the inner timeout is bypassed.
|
|
_OUTER_TIMEOUT_GRACE_SECONDS = 5
|
|
# consent answer -> (ElicitResult action, metric); anything else declines.
|
|
_ANSWER_RESULTS = {"accept": ("accept", "accepted"), "cancel": ("cancel", "errors")}
|
|
|
|
def __init__(self, server_name: str, config: dict, owner: Optional["MCPServerTask"] = None):
|
|
self.server_name = server_name
|
|
# Default 5 min mirrors the gateway approval default so async surfaces
|
|
# (Telegram, Slack) have time to respond.
|
|
self.timeout = _safe_numeric(config.get("timeout", 300), 300, float)
|
|
# Back-reference for the agent's contextvars snapshot; optional so the
|
|
# handler stays unit-testable in isolation.
|
|
self.owner = owner
|
|
self.metrics = {"requests": 0, "accepted": 0, "declined": 0, "errors": 0}
|
|
|
|
def session_kwargs(self) -> dict:
|
|
"""Kwargs to pass to ClientSession for elicitation support."""
|
|
return {"elicitation_callback": self}
|
|
|
|
def _result(self, action: str, metric: str):
|
|
"""Count *metric* and return ``ElicitResult(action)`` (accept carries empty content)."""
|
|
self.metrics[metric] += 1
|
|
return _core.ElicitResult(action=action, content={}) if action == "accept" else _core.ElicitResult(action=action)
|
|
|
|
def _consent_thunk(self, message: str, description: str) -> Callable[[], str]:
|
|
"""Sync consent call, replaying the agent's contextvars snapshot when the
|
|
owner captured one: the recv-loop task does NOT inherit them, and
|
|
gateway-platform detection needs them. ``Context.run`` executes a
|
|
context once, so it is copied per elicitation."""
|
|
from tools.approval import request_elicitation_consent
|
|
|
|
kwargs = {"timeout_seconds": int(self.timeout), "surface": f"mcp-elicitation/{self.server_name}"}
|
|
captured = getattr(self.owner, "_pending_call_context", None) if self.owner else None
|
|
if captured is None:
|
|
return lambda: request_elicitation_consent(message, description, **kwargs)
|
|
return lambda: captured.copy().run(request_elicitation_consent, message, description, **kwargs)
|
|
|
|
async def __call__(self, context, params):
|
|
"""SDK elicitation callback (``ElicitationFnT``). Returns ElicitResult or ErrorData."""
|
|
self.metrics["requests"] += 1
|
|
|
|
# URL-mode (OAuth, payment) would need a browser + waiting for
|
|
# notifications/elicitation/complete — not implemented; decline cleanly.
|
|
if getattr(params, "mode", "form") == "url":
|
|
logger.info(
|
|
"MCP server '%s' requested URL-mode elicitation; declining (URL-mode elicitation not implemented)",
|
|
self.server_name,
|
|
)
|
|
return self._result("decline", "declined")
|
|
|
|
message = getattr(params, "message", "") or f"MCP server '{self.server_name}' is requesting your approval"
|
|
# ``requestedSchema`` on mcp 1.x, ``requested_schema`` on 2.0 (pydantic
|
|
# aliases don't apply to attribute access) — read both or the user is
|
|
# asked to approve without seeing which fields the server wants.
|
|
schema = getattr(params, "requestedSchema", None) or getattr(params, "requested_schema", None) or {}
|
|
description = _format_elicitation_schema_summary(schema, self.server_name)
|
|
logger.info("MCP server '%s' elicitation request: %s", self.server_name, _sanitize_error(message)[:200])
|
|
|
|
# Lazy import avoids import-order coupling with early-bootstrap tools.approval.
|
|
try:
|
|
invoke_consent = self._consent_thunk(message, description)
|
|
except Exception as exc: # pragma: no cover -- defensive
|
|
logger.error("MCP server '%s' elicitation: approval system unavailable: %s", self.server_name, exc)
|
|
return self._result("decline", "errors")
|
|
|
|
# Offload the sync consent flow to a thread — inline it would freeze the
|
|
# MCP loop and every other RPC on this session.
|
|
try:
|
|
answer = await asyncio.wait_for(
|
|
asyncio.to_thread(invoke_consent), timeout=self.timeout + self._OUTER_TIMEOUT_GRACE_SECONDS,
|
|
)
|
|
except asyncio.TimeoutError:
|
|
logger.warning("MCP server '%s' elicitation timed out after %ds", self.server_name, int(self.timeout))
|
|
return self._result("cancel", "errors")
|
|
except Exception as exc:
|
|
logger.error("MCP server '%s' elicitation failed: %s", self.server_name, exc, exc_info=True)
|
|
return self._result("decline", "errors")
|
|
|
|
return self._result(*self._ANSWER_RESULTS.get(answer, ("decline", "declined")))
|